The IBM RISC System/6000 processor: Hardware overview

A highly concurrent superscalar second-generation family of RISC workstations and servers is described. The RISC System/6000* family is based on the new IBM POWER (Performance Optimization With Enhanced RISC) architecture; the hardware implementation takes advantage of this powerful RISC architecture and employs sophisticated design techniques to achieve a short cycle time and a low cycles-per-instruction (CPI) ratio. The RS/6000 CPU features multiple-instruction dispatch, multiple functional units that operate concurrently, separate instruction and data caches, and zero-cycle branches. In this superscalar implementation, at a given cycle the equivalent of five operations can be executed simultaneously (a branch, a condition-register operation, and a floating-point multiple-add). The RS/6000 family supports the IBM Micro Channel architecture as well as high-speed serial optical links to provide a high-bandwidth I/O subsystem.